Reverse Polish Notation (RPN) is a mathematical notation and entry logic for calculators that has some advances over the more common algebraic notation. This is why many scientists and engineers prefer RPN-based calculators. Devices are, however, expensive and available from a small number of companies only (e.g. HP and SwissMicros). The selection of virtual calculators with RPN for desktop computers is limited, too. The TRURL project provides libraries for creating virtual calculators in Object Pascal and pre-compiled apps for macOS, Windows and other operating systems.

With immediate effect, TRURL's RPN Engine for Lazarus and Free Pascal is available. It is a collection of Object Pascal types, classes and procedures that can be used as a foundation for virtual RPN calculators. The RPN Engine supports the creation of both text-mode and GUI-based calculators.

More information is available from

trurl.sf.net. The site also provides TRURL A, a very simple (but fully functional) RPN calculator that shows, how easy it is to create a calculator with Lazarus and the RPN Engine.

All software of the TRURL repository is available with a BSD license, making it freely available for both free open source and commercial projects.